Nitrox instead of air for lower DCS risk?

[Derek S]

BigTuna -

I've noticed you poking around the NEUE board as well, so I'll give you our thoughts on it:

Dives 0-100 FFW/FSW: 32% EAN

While I can't say if using nitrox would lessen the chances of a diver taking a DCS hit, I'm inclined to say that breathing a gas with a higher o2 content *should* be helping you offgass excess nitrogen faster than using regular 21%.

As always, plan your dive, dive your plan, do a proper ascent with requisite stops, and you should be fine.

 

[RiverRat]

Nope. You're thinking of DCI - Decompression Illness. DCS - Dcompression Sickness is just the bends. DCI includes DCS as well as AGE and the other lung over expansion maladies. DCI is a confusing term and I see no need to ever use it. Now, it's even confusing people as to the meaning of DCS.

Sorry......had it backwards

 

[DandyDon]

Sorry......had it backwards

Yeah - like the man said: "DCI is a confusing term and I see no need to ever use it. Now, it's even confusing people as to the meaning of DCS."

The only reason I can see for using the more inclusive DCI is to refer to noticed problems not yet diagnosed, but the term is too similar. Why couldn't they call it something different, like "Problematic Ascent Injury"?

Thanks for the help, young fella (I'm 64) and everybody else. I think that sums up the concensus pretty well, if I add keeping the computer on an air setting. It can't hurt and might help some. In addition I run the computer (Cobra) at one level of conservatism. Overkill? I don't want to find out--I'm having too much fun.

Incidentally, if this practice only helps "some" in holding DCS at bay, I imagine that's because the percent of nitrogen in EANx is only around 15% less than in air. That's an improvement, but it's not stellar.

If/when I find my gas consumption gets low enough that I'm running up against the no-deco limit, that would be a happy day. I suppose then I'd consider using a nitrox setting and using the extended bottom time. Dunno. Not totay's problem.

Your air consumption will get better if you can get frequent practice and relax. I've also seen divers get a lot better when they bought more comfortable mouthpieces for their regs.

A lot of mine depends on where I'm diving...
>> In the Bay Islands where Nx is $100 for all you want for a week, I'll use it on every dive, and use 36% on shallow dives just to help flush my blood gases of N2.
>> For NC and St.Lawrence wreck dives back to back, Nx all the way.
>> In the Florida Keys, I'll use Nx on a deeper wreck dive that I could really do on Air okay, as my 80 cf tank won't last that long at 100 ft anyway - but the computer loading is much lower with Nx on the dives. At $6 a tank, I don't bother on 40 ft deep reef dives.
>> In Cozumel, at $10 a tank, I become less interested unless we are doing 2 deeper dives in a row, then I'll use Nx on the second dive.
>> In Calf, I try to explain what Nx is.

 

[BigJetDriver]

Nope. You're thinking of DCI - Decompression Illness. DCS - Dcompression Sickness is just the bends. DCI includes DCS as well as AGE and the other lung over expansion maladies. DCI is a confusing term and I see no need to ever use it. Now, it's even confusing people as to the meaning of DCS.

Actually, Walter, even the experts are confused and confusing about the choice of DCI or DCS. The best advice I have heard on the subject comes from a noted expert in the field: "Just don't use the two in the same article."

 

[BigTuna]

BigTuna -

I've noticed you poking around the NEUE board as well, so I'll give you our thoughts on it:

Dives 0-100 FFW/FSW: 32% EAN

While I can't say if using nitrox would lessen the chances of a diver taking a DCS hit, I'm inclined to say that breathing a gas with a higher o2 content *should* be helping you offgass excess nitrogen faster than using regular 21%.

As always, plan your dive, dive your plan, do a proper ascent with requisite stops, and you should be fine.

Thanks, Derek. Some questions...

- With your recommendation of 32% for 0-100 ft dives, it looks like you're keying on a max PO2 of 1.3. So why wouldn't you say 36% EAN for 0-80 ft dives? Or 40% EAN for 0-70 ft dives? There'd be no problem with oxygen exposure (not for me, anyway).

- If you look above at Don's remarks, he uses 36% to flush his system, but he doesn't regularly use EAN shallower than 40 ft. Would you suggest using it on dives above 40 feet? If so, what blend?

- What do you mean by "our thoughts"? Is there an underlying reference you have in mind and could direct me to?

 

[Derek S]

Thanks, Derek. Some questions...

- With your recommendation of 32% for 0-100 ft dives, it looks like you're keying on a max PO2 of 1.3. So why wouldn't you say 36% EAN for 0-80 ft dives? Or 40% EAN for 0-70 ft dives? There'd be no problem with oxygen exposure (not for me, anyway).

- If you look above at Don's remarks, he uses 36% to flush his system, but he doesn't regularly use EAN shallower than 40 ft. Would you suggest using it on dives above 40 feet? If so, what blend?

- What do you mean by "our thoughts"? Is there an underlying reference you have in mind and could direct me to?

No problem. I'll answer as best I can, and say that the NEUE board is also a great source as well.

Let me preface my response by stating that my recommendations are based on the GUE mindset. I am not pushing it, just offering it as an option based on what I've seen your goals to be. :14:

- 32% is the most readily available EAN mix. Depending on where you are, getting a 36% or 40% mix might be quite a bit more expensive, and *in theory*, offer no tangible benefits over 32%. Again, planning your dive, and diving your plan is the best way to combat DCS. On dives where your SAC rate is going to be the determining factor instead of NDLs, I just can't justify the extra expense of a higher o2 mix than 32%. Another thing to keep in mind is that you have PPo2 limits for individual dives, as well as over a 24-hour period. It's just as dangerous to exceed it over the course of a day as it is to break MOD on a single dive.


- Flushing oneself with a higher % of EAN is not a bad idea, but if one plans properly and does a proper ascent coupled with the requisite stops, it *should* be unnecessary. Again, to each their own.

- "Our thoughts" as in the NEUE team standards and in a larger range, the GUE standards. I'm not saying it is the way to go, just something to think about.

 

[DandyDon]

On my last dive trip, Florida Keys in December, we only did 4 wreck dives with which I used Nx - the rest were shallow reefs. I set my primary computer for the blend on each of those, but had 2 more of the same brand in my pocket left on air settings. It was interesting to see the overall N2 loading difference at the end of the days we did wrecks.

 

[ArcticDiver]

Thanks for the help, young fella (I'm 64) and everybody else. I think that sums up the concensus pretty well, if I add keeping the computer on an air setting. It can't hurt and might help some. In addition I run the computer (Cobra) at one level of conservatism. Overkill? I don't want to find out--I'm having too much fun.

Incidentally, if this practice only helps "some" in holding DCS at bay, I imagine that's because the percent of nitrogen in EANx is only around 15% less than in air. That's an improvement, but it's not stellar.

If/when I find my gas consumption gets low enough that I'm running up against the no-deco limit, that would be a happy day. I suppose then I'd consider using a nitrox setting and using the extended bottom time. Dunno. Not totay's problem.

Glad to see another mature diver in the sport That said here are the facts in a couple brief sentences:
-Nitrox by itself does not reduce DCS risk. How it is used can reduce DCS risk. For a given length dive using Nitrox instead of Air will reduce the amount of nitrogen in your body. So, to the extent that nitrogen loading affects DCS the likelyhood of DCS is reduced.
-However, if the reduced nitrogen loading is used to extend dive time then the DCS risk becomes the same as if air were used and the dive time were shorter.
-Nitrox increases the risk of oxygen toxicity. It also increases the likelyhood of airway and lung irritation. These can be minor and no problem. Or the irritation can cause serious effects. So, like most things in life there are trade-offs.
-The safest way to use Nitrox is to dive it for what it is: Nitrox. It is not air so do not use air tables. That is the lazy person's way and can get you in trouble. Those who recommend using air tables either don't understand the gas themselves, or they don't think others can. Understand the gas you are breathing, or don't use it.

Using an approprately mixed gas for diving is a great convenience and can be a great safety enhancement. But, only if it is thoroughly understood.

As for me? I use appropriately mixed nitrox at every opportunity. I monitor the side-effects and to be reasonably sure the benefits always outway the costs.

Good diving.

 

[Jordan]

Air is simply dangerous for diving (Jordan ducking and hiding). The only thing I use compressed air for is to fill up my car tires and even they usually get nitrox fills (only because of convenience).

OK OK, I would be fine with air if I were in a swimming pool or doing a dive shallower than 35 feet - but that's about it. I also have access to nitrox just as easily and as cheaply as air, so....

 

[Derek S]

Artic brings up some VERY vaild and important points.

Although I'm nowhere near mature (just ask my wife ), it is great to know that I will still be able to enjoy this sport I love for decades to come.

As with understanding the EAN tables, divers should be aware that those tables were cut using data from young, healthy in-shape divers, and that each individual is different. What might work for me could be completely different for someone else and of course, vice-versa.